"I don't really have a prediction because I've never seen the guy fight that's facing Conor McGregor-from what I know he's a hell of a guy that's on the ground-hell of a grappler-and he can wrestle.

"But, the fans want to see you stand up and fight. That's what the fans like to see. But, Conor McGregor, he's a tough competitor, like I said before Conor McGregor's not gonna back down from anyone, he's not scared, he's a warrior."

Mayweather invited McGregor to train for the fight at his own Mayweather Boxing Club - but McGregor isn't interested. The UFC star issued a profane response to Mayweather on Twitter.